The present invention relates to a composite injector for introducing a first chemical product which becomes corrosive when heated above a certain temperature into an enclosure containing a second chemical product which when chemically combined with said first chemical product, produces a highly exothermic chemical reaction. More particularly, the invention relates to an injector suitable for introducing sulfur hexaflourine into an environment containing molten lithium.
The utilization of stored chemical energy to generate heat energy in order to power Rankine cycle power plants is well known. One such system is described in U.S. Pat. No. 4,959,566, entitled "LITHIUM-SULFUR HEXAFLUORIDE MAGNETOHYDRODYNAMIC POWER SYSTEM CONFIGURATIONS AND SYSTEM DESIGN CONSIDERATIONS," Sep. 25, 1990. Another such system is described in "LITHIUM-SULFUR HEXAFLUORIDE MAGNETOHYDRODYNAMIC POWER SYSTEM," Feb. 24, 1987.
One type of injector for introducing SF6 into an environment of liquid lithium employs a two-part assembly comprising a tungsten tube brazed within a Hastalloy housing. The SF6 flows through the tungsten tube. An air gap between the tube and the housing partially insulates the tube from the heat migrating from the lithium bath through the housing. One problem with this type of injector is that it allows too much heat to migrate into the flow path. This allows SF6 flowing though the tungsten tube disassociates into fluorines and sulfides at elevated temperatures. The fluorines attack the tungsten causing spallation of the tungsten. Once the tungsten degrades, the less capable Hastalloy quickly follows suit leaving a hole in the boiler for lithium to escape. Another failure mode is where the flame plume at the front of the injector causes the Hastalloy housing to melt away, providing a path for the lithium to surround the tungsten insert. The hot lithium further heats the SF6, causing certain failure of the tungsten insert from corrosive action by the disassociated SF6.
These problems result from the fact that metals conduct heat well and corrode rapidly at high temperatures. Another problem with metal based injectors used in conjunction with these systems is that metals have a high range of coefficients of thermal expansion. This is a problem for assemblies comprising components manufactured of different metals each having a different coefficient of thermal expansion because the components are vulnerable to cracking due to thermally induced stresses.
Therefore, there is a need for a non-metallic based injector suitable for use in an SF6/lithium power system that is more temperature and chemical resistant than would be a metallic based injector.